Field of the Invention
One disclosed aspect of the embodiments relates to an imaging apparatus and an imaging system.
Description of the Related Art
An imaging apparatus typically includes a photoelectric conversion portion, region, or circuit, that generates electric charge by photoelectrically converting incident light, and a floating diffusion portion, region, or circuit, that accumulates the electric charge, in which a pixel outputs an optical signal based on the potential of the floating diffusion portion. Furthermore, a configuration including an amplification portion, region, or circuit, that amplifies the optical signal output by the pixel is known as an example of the imaging apparatus.
In an imaging apparatus described in Japanese Patent Laid-Open No. 2012-257029, a multi-stage amplification portion amplifies an optical signal output by a pixel. Specifically, the first stage of the amplification portion amplifies an optical signal output by a pixel, and the second stage of the amplifier amplifies the signal amplified by the first stage of the amplification portion.
Moreover, in the imaging apparatus, the blackening phenomenon in which a portion having a large amount of light, which should be originally expressed as white that is highly bright, is reduced in brightness or blackens may happen when a subject having a large amount of light is photographed.
Japanese Patent Laid-Open No. 2014-212423 describes a configuration, including a limiter circuit that limits the output of an amplification portion that amplifies an optical signal output by a pixel, to reduce the blackening phenomenon.
Moreover, Japanese Patent Laid-Open No. 2007-201550 describes a configuration including a first amplifier circuit and a second amplifier circuit connected to an output node of the first amplifier circuit, the configuration including a limiter that limits the output of the first amplifier circuit and a limiter that limits the output of the second amplifier circuit.
Moreover, an imaging apparatus is known which includes an effective pixel that outputs a signal based on electric charge generated by photoelectric conversion, and a reference pixel that outputs a reference signal without performing photoelectric conversion.
As such an imaging apparatus, there is an imaging apparatus described in Japanese Patent Laid-Open No. 2012-253740. Japanese Patent Laid-Open No. 2012-253740 describes the imaging apparatus in which a fully differential amplifier circuit outputs a signal amplified from a difference between a signal output by the effective pixel and a signal output by the reference pixel.